AD 2020-12-07 Created After The Loss of A USMCR KC-130T

The FAA is adopting a new airworthiness directive (AD) for certain Hamilton Sundstrand Corporation (Hamilton Sundstrand) 54H60 model propellers. This AD was prompted by the failure of a propeller blade that resulted in the loss of the airplane. This AD requires initial and repetitive eddy current inspections (ECIs) of the affected propeller blades and replacement of the propeller blades that fail the inspection. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective July 20, 2020.

Supplementary Information: The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to certain Hamilton Sundstrand 54H60 model propellers. The NPRM published in the Federal Register on January 28, 2020 (85 FR 4916). The NPRM was prompted by a report of the separation of a 54H60 model propeller blade installed on a United States Marine Corps Reserve (USMCR) KC-130T airplane during a flight in July 2017.

The USMCR investigation of this event revealed the Hamilton Sundstrand 54H60 model propeller blade separated due to corrosion pitting and a resultant intergranular radial crack that was not corrected at the last propeller overhaul. From this intergranular crack, a fatigue crack initiated and grew under service loading until the Hamilton Sundstrand 54H60 model propeller blade could no longer sustain the applied loads and ultimately the blade separated. The separation of the blade resulted in the loss of the airplane and 17 fatalities. The investigation further revealed that 54H60 model propeller blades manufactured before 1971 are susceptible to cracks of the propeller blade in the area of the internal taper bore. The applicability of this AD is therefore limited to those Hamilton Sundstrand 54H60 model propellers blades with a blade serial number below 813320, which are those propeller blades manufactured before 1971.

The NPRM proposed to require initial and repetitive ECIs of the affected propeller blades and removal from service of any blades that fail these inspections. Propeller blade taper bore cracks, if not detected, could result in failure of the propeller blade, blade separation, and loss of the airplane.

The FAA is issuing this AD to address the unsafe condition on these products.

FMI: www.regulations.gov